Adaptive Front Lighting is being offered by several automotive manufacturers. In AFL, the vehicle's left and right headlamps are controlled together to adapt or adjust the front beams to the momentary driving situation. For example, when turning to the left or right, a controller determines the angle of turning and causes a part of the headlamp—usually the projection lens—to swivel by a corresponding swivel angle, so that the beam also swivels. In this way, the low beam does not remain stationary relative to the vehicle as is the case for conventional headlamps, but it is directed deliberately ‘into’ the turn.
While such swiveling headlamps offer the advantage of being able to actively control the headlamp beam direction when turning into a corner so as to optimally illuminate the actual direction of travel, they also have a number of disadvantages. Firstly, if the vehicle is being turned into a ‘sharp’ corner, e.g. when turning off the road at a right angle into a side-road or when performing a U-turn, the outer beam ‘turns in’ towards the body of the vehicle and this effectively blocks a part of that beam. For example, when turning to the extreme left, the right beam is in many cases at least partially obstructed by the car body. This effect is largely unavoidable in conventional arrangements since, for various reasons, the body of the headlamp cannot extend beyond the body of the vehicle, and the projection lens is positioned inside the headlamp (behind the front glass cover). Secondly, any moving parts such as motors or actuators required to physically swivel the moveable parts of the headlamp arrangements are vulnerable to damage or failure.
The first AFL arrangements used xenon or halogen lamps with a projection lens or reflector to image the single light source. However, developments in the field of light-emitting diode technology have led to very bright high-power LEDs that are suitable for use in automotive lighting applications. In place of a single xenon or halogen lamp, an array or matrix of LEDs can be used to generate a front beam. The ‘swivel’ effect can be obtained by using a suitable projection lens and activating only those LEDs that are required to generate the beam at any given time. For example, to swivel or direct the beam to the right, those LEDs on the left-hand side of the optical axis are turned on while the others are turned off. However, a well-defined beam can only be obtained using the LEDs close to the optical axis. The light originating from the light sources further away from the optical axis, namely those light sources used to generate the extreme swiveled beam, is subject to aberration, and the resulting beam is poorly defined. To obtain a well-defined beam in keeping with ECE and SAE regulations, therefore, the projection lens must be designed to compensate for this aberration, but such lens design generally presents a high cost factor.
Therefore, it is an object of the invention to provide an improved and economical and robust dynamic headlamp arrangement which avoids the problems described above.